Phases

Participants in clinical trials can play a more active role in their own health care, gain access to new research treatments before they are widely available, and help others by contributing to medical research. Treatment trials, test new treatments, new combinations of drugs, or new approaches to surgery or radiation therapy. Prevention trials look for better ways to prevent diseases in people, who have never had the disease or to prevent a disease from returning. These approaches may include medicines, vitamins, vaccines, minerals, or lifestyle changes. Screening trials test the best way to detect certain diseases or health conditions. Quality of Life trials (or Supportive Care trials) explore ways to improve comfort and the quality of life for individuals with a chronic illness. Clinical trials are conducted in phases.

The trials at each phase have a different purpose and help scientists answer different questions:

Phase I trials

Researchers test a new drug or treatment in a small group of people (20-80) for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.

Phase II trials

The study drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.

Phase III trials

The study drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.

Phase IV trials

Post marketing studies delineate additional information including the drug's risks, benefits, and optimal use.